The invention relates to the direction finding techniques for use with compressive receivers.
Direction finding techniques used with conventional radio systems are well known in the art. For example, see "Radio Engineer's Handbook" by F. E. Terman published 1943 starting at page 872. Additionally, compressive receivers are well known in the art, as exemplified by U.S. Pat. No. 2,882,395. Typical prior art direction finding equipment employs two or more receivers which are carefully designed so that each of the receivers used in the direction finding equipment has uniform amplitude and phase shift characteristics. However, substituting compressive receivers for the conventional receivers used in direction finding equipment presents a major drawback in that the dispersive delay line employed in the compressive receivers need be ideally balanced to achieve meaningful results. Such balanced dispersive channels would be very difficult to achieve.
It was therefore one object of the present invention that a direction finding compressive receiver be provided which is insensitive to the lack of channel balance typically imposed by a pair of dispersive channels.
It is yet another object of this invention to provide a direction finding compressive receiver which employs but one dispersive channel.
It is still another object of this invention that a direction finding compressive receiver be comparable to at least two antenna for direction finding purposes yet require but one dispersive delay line channel.
It is still yet another object of this invention to provide a direction finding compressive receiver of simpler construction than those which might be suggested by the prior art.
The foregoing objects are achieved as is now described. A direction finding compressive receiver is provided with outputs from at least two antennas. The antenna outputs are applied to separate mixers which also receive the output from a common swept local oscillator. The outputs of the mixers are selectively delayed prior to being connected in common to the input to a dispersive delay line. The output of the delay line is coupled to the inputs of a comparison circuit, at least one of the inputs being coupled via another delay line.
The advantage of the invention both as to its construction and mode of operation, in the prefered mode of use, will be readily appreciated by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals refer to like parts throughout the drawings.